This invention relates generally to lever mechanisms for circuit breakers and more particularly to a retractable lever mechanism for use with circuit breakers disposed in an electrical enclosure.
A common circuit breaker has a pivot handle which moves linearly between an on and an off position. The pivot handle is connected to the movable contacts within the circuit breaker assembly through a spring powered, over center toggle device. When the handle is moved into the on position, the movable contacts close upon themselves completing an electrical circuit. When the handle is moved into the off position, the movable contacts separate from each other interrupting the electrical circuit. In response to certain overcurrent conditions, the contacts open automatically causing the handle to move to an intermediate position.
Often in application, these circuit breakers are mounted behind a door in an electrical enclosure. Typically in these installations, the pivot handle of the circuit breaker will protrude through an opening in the door where it can be operated directly. This configuration leaves the circuit breaker exposed to the environment where damage to the components of the breaker may result. To solve this problem, circuit breakers are now equipped with an interface between the operating handle and the outside of the electrical enclosure whereby the circuit breaker is sealed from the hazards of the environment. This interface often is a flange-mounted, linearly movable, pivot handle operator.
While the typical pivot handle operator provides the desired interface between the person operating the breaker and the breaker itself, it has been found that the lever is often difficult to use. This problem is attributable to safety requirements and size constraints which have necessitated that the handle operator lever be limited to a small size. In particular, the small amount of leverage that can be generated from the short lever makes it difficult for the operator to overcome the spring force which loads the over-center toggle device of the breaker when the operator switches the breaker between the on and off positions. Typically, operators use crow-bars or like instruments in conjunction with the operator handle to increase the amount of leverage that may be applied to these devices. This results in exposing the device as well as the operator to potential harm.
A need exists for a circuit breaker handle operator which will provide increased leverage while still remaining small enough to fulfill the industries safety requirements and size constraints.